Martin Flannery

Martin Flannery, the former Sheffield Hillsborough MP for 18 years, who has died aged 88, was "Mr Indignant Leftwinger", a hard-left Labour MP who most frequently began his Commons questions with: "Is it not a disgrace ..." A deeply emotional man, he had plenty to be indignant about, initially as a communist and later as a founder member of the Campaign group. He detested American imperialism, British misdeeds in Northern Ireland and (after Khrushchev's 1956 revelations) Stalinist repression. He was anti-EEC and pro-Arab.

He fought his corner as a self-conscious defender of the working class in whatever theatre he operated: as a teacher and headmaster in his native Sheffield, as a kamikaze candidate of the Campaign group against moderate Labour men in the Parliamentary Labour party. As the left's candidate in the 1979 election for chief whip, he won 44 votes against Michael Cocks's 88.

Because Flannery's convictions were so strongly rooted, uprooting them was a wrench. Being of Irish-Catholic origins and a devout Republican, it was a shock to him in 1984 when, on a Labour delegation to Northern Ireland, he discovered that even Sinn Féiners did not want an immediate withdrawal of British troops, fearing a Catholic bloodbath. He could only occasionally manage to coat his anti-Tory attacks with humour, as when he said of Nicholas Ridley that he "can actually strut sitting down".

The son of a steel storeman, Flannery attended the local De La Salle Roman Catholic grammar school and teacher training college. Serving in the 1st Battalion of the Royal Scots Corps during the war, he was wounded in Burma. As an NUT radical after the war, he worked his way up to become headteacher of Crookesmoor junior school (1969-74). He gave up this post to become, in February 1974, MP for the Hillsborough seat in north-west Sheffield.

In the Commons, where Labour had unexpectedly become the biggest party, Flannery demanded a free pardon for the Shrewsbury Two, who were jailed after the 1972 national building workers' strike became the focus of mass trade union protests. He opposed Harold Wilson's cuts and anti-inflationary wage policy, and when Wilson stepped down in 1976 he backed Michael Foot, rather than James Callaghan, as his successor. He voted against the 1982 Falklands war, instead of abstaining as requested. That same year he switched from the moderate-left Tribune group to become a founder member of the hard-left Campaign group.

Because Flannery's changes of posture stepped on many toes, he encountered increasing opposition. Bob Clay and Joan Maynard - both "troops outers" - tried unsuccessfully to block his continuing as chairman of the PLP's Northern Ireland group in 1984. In his constituency, he had to fight off a moderate challenger, Clive Betts. He battled on, defending comprehensive schools and opposing defence estimates and the "unworkable" Prevention of Terrorism Act until he stepped down in 1992. He is survived by Blanche, his wife of 57 years, a son and two daughters.

· Martin Henry Flannery, politician and teacher, born March 2 1918; died October 16 2006